Understanding Process Equipment for Operators and Engineers

Norman Lieberman

• Publisher: Elsevier
• Year: 2019
• Print ISBN: 9780128161616
• eBook ISBN: 9780128161623
• Topic: Technology & Engineering
• Subtopic: Chemical & Biochemical Engineering
• Index: Technology & Engineering

Understanding Process Equipment for Operators and Engineers explains how process equipment functions. As problems often arise in plants that must be solved by unit engineers, this book offers successful solutions and methods for their implementation. The concepts explained are based on Norm Lieberman's personal, hands-on experience. Like you, Norm attended a university and was exposed to technical seminars which did not always provide the needed solutions. In this text, you will learn the functioning of a variety of equipment types, including Fired Heater Draft, Centrifugal Pump Head, Distillation Tray Efficiency, Vacuum Jets, Recip Compressors, Steam Turbines, Thermosyphon Circulation Reboilers and Air Cooler.- Includes methods and procedures on how to make field measurements- Outlines fire heater principles and operation and how they develop draft- Describes distillation column operation and methods to increase their efficiency- Includes computer modeling and provides use case examples

1

Basics of Process Operations and Engineering

Abstract

Optimizing excess air in a fired heater. Minimizing NO_x emissions. Air preheaters can save energy but reduces heater capacity. Steam turbines convert the heat content of the steam to work. Using superheated steam to a turbine reduces its horsepower output. Increasing reboiler duty can stop a distillation tower from flooding. The latent heat of steam is reduced at higher pressure. Decreasing the molecular weight of gas promotes surge in a centrifugal compressor.

Keywords

Latent heat; Surge; Compressor; Distillation; Heat transfer; Thermodynamics; Air preheat

The truth is you’ve wasted 4 years in University qualifying for an engineering degree or have wasted 2 years in an operator training class. That's not my fault. But now, as a process engineer in a refinery, or as an operator in a petrochemical complex, you need to understand how pumps, compressors, heat exchangers, distillation towers, air coolers, fired heaters, steam boilers, turbines, and vacuum ejectors actually work to do your job.

The reason you did not understand your professor about how process equipment works is that he didn’t understand it himself. Everything I write is based on my own experience and field observations. For example:

1. 1. Increasing excess combustion air in a fired heater will cool off the tubes in the firebox, but increase the heater absorbed process duty.
2. 2. Nitric oxides (NO_x) can be reduced by increasing air flow to the secondary air register and reducing air flow to the primary air register.
3. 3. Preheating combustion air to a heater will often reduce its heat absorption capacity.
4. 4. The energy to spin a steam turbine does not come from the steam's pressure, but from the steam's heat content.
5. 5. But, superheating steam to a steam turbine will cause the turbine to slow down.
6. 6. A steam vacuum ejector is really a multistage gas compressor, but there are no moving mechanical components.
7. 7. One way to stop a distillation tower from flooding is to increase the reboiler duty.
8. 8. With a constant reboiler duty, lowering a distillation tower's top temperature with more reflux increases the vapor flow.
9. 9. Ancient bubble cap trays have a better tray fractionation efficiency than modern trays, and also a lower pressure drop.
10. 10. When starting a centrifugal pump, monitor the pump suction pressure, not its discharge pressure.
11. 11. The feet of head produced by a centrifugal pump does not vary with the density of the liquid pumped.
12. 12. Increasing the load on an ordinary alternating current motor-driven pump does not affect its speed.
13. 13. Centrifugal, motor-driven American pumps, run 20% faster than European pumps. Why? Because they are American pumps.
14. 14. A butane reboiler will have more capacity, if its tubes are pitted and corroded, than a reboiler with brand new tubes.
15. 15. A tiny amount of air or CO₂ in steam will reduce a steam reboiler, or a steam turbine surface condenser, capacity by 50%.
16. 16. The latent heat of condensation of steam increases a lot as the steam pressure is reduced.
17. 17. The auto-ignition temperature of gasoline is much higher than tar.
18. 18. Hydrogen heats up as it expands, but all other gases cool off, as they expand.
19. 19. Centrifugal compressors surge when the gas molecular weight is reduced.
20. 20. Partly closing a cooling water outlet valve from an exchanger elevated 60 ft above grade can increase its water flow.
21. 21. A rising level in a boiler can cause the boiler's indicated level to be reduced, and the boiler feed water level control valve to open, even though the water level is already excessive.
22. 22. A gas flow meter will read a reduction in gas flow rate, even though the actual volume of gas flow has not changed, if the gas molecular weight is reduced.
23. 23. A pressure above atmospheric can develop in the upper portion of a heater's firebox, even though a substantial vacuum exists in the lower portion.
24. 24. Thermosyphon circulation rates may be reduced, as the exchanger heat input increases.
25. 25. An effective way to improve a distillation tower fractionation efficiency is to reduce the tower's operating pressure.
26. 26. The motor amps increase with molecular weight for a centrifugal compressor, but decrease with a higher molecular weight for a reciprocating compressor.
27. 27. Fouled fin tubes on a forced draft air cooler which greatly reduces cooling air flow through the tube bundle does not increase the amp load on the fan's motor driver.
28. 28. The outlet pressure of a heat exchanger can be higher than the inlet pressure, even though both pressure points are at the same elevation.
29. 29. Closing a by-pass valve around a condenser will usually reduce the condenser's upstream pressure.

The preceding points are all somewhat counterintuitive. I’ll explain the process basis for each of them in the following chapters. The application of these and other concepts I have discussed in subsequent chapters have led to the solution of many process problems and enhanced the capacity and efficiency of hundreds of process units.

I think most people are like me. I find it difficult to learn new stuff by reading, listening, or just watching. But, when I apply my own hands, and my own mind, to a particular problem, I remember and understand the solution for the rest of my life. And, as someone, who has been practicing solving process engineering problems in the field, without any hiatus, since 1964, that's a lot of learning opportunities.

We are fortunate to work in an industry where the nature of the equipment has barely changed in the past six decades. Becoming a proficient process operator, or process engineer, is still largely a matter of time and determination. And, I suspect, that will always be true as long as we try to alter the nature of hydrocarbons, minerals, water, and a...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Author Note
• Introduction: An Act of Creation
• General Introduction
• 1: Basics of Process Operations and Engineering
• Part 1: Fractionation
• Part 2: Hydraulics
• Part 3: Heat Transfer
• Part 4: Revamping Process Units
• Part 5: Fired Heaters
• Part 6: Vacuum System
• Part 7: Steam Turbines and Ejectors
• Part 8: Rotating Equipment
• Part 9: Reciprocating Compressors and Piping Vibrations
• Part 10: Problems in Process Operations and Engineering Principles
• Part 11: Plant Safety
• Part 12: Caring for Our Environment
• Index